The contents of datablocks can be changed interactively with several commands, for example Db_set_data, Db_set_zone and Db_set_atom. However, we recommend a different approach unless you really know what you are doing. A safer method is to write the datablock out into the computer file-system (use Write_formatted), edit it with your favourite editor, and read it back in again (use Read_formatted). Note that formatted data blocks are read back under formatted control!